Simple Harmonic Motion and frequency of vibration

When a 63 kg person climbs into a 1040 kg car, the car's springs compress vertically by 3.3 cm. What will be the frequency of vibration when the car hits a bump? Ignore damping.

Here is the FBD I have drawn:

http://img276.imageshack.us/img276/6189/fbdcc2.png [Broken]

Im not even sure if this is really right...

I really just don't know where to begin with this. I added the masses together...and I know I have an x value of 3.3 cm. I don't know how to conceptualize this so that the FBD makes sense...any tips or hints are appreciated

Staff: Mentor

Are you familiar with the Simple Harmonic Motion of a mass on a spring? If not, that's what you should study before tackling this problem. Here's a start: http://hyperphysics.phy-astr.gsu.edu/hbase/shm.html" [Broken]